Hydrocarbons, such as crude oil, may be refined to produce various products, such as jet fuel, gasoline, diesel fuel, paraffins, kerosene, naphtha, lubricating oils, asphalts, fuel oil, and liquefied petroleum gases (LPGs) such as propane and butane. Refining generally refers to a group of processes that treat, chemically change, and blend hydrocarbons. The refining process for crude oil generally breaks apart the heavier or more dense hydrocarbon chains of the crude oil at various pressures and temperatures to produce various “major cuts” or raw hydrocarbon fractions, ranging from heavy residuals to fuel oils to lighter or less dense gasoline and petroleum gas. Some refining processes may result in finished products such as diesel fuel. Other refining processes may result in intermediate products, such as fuel oil, that require further processing to produce a finished product. For example, a fuel oil may be refined further to change its chemical components in a way suitable for use in blending gasoline.
Refining methods as well as techniques for testing refinery product properties may be suitably configured to accommodate the relatively complex composition of crude oil that may be source or even batch dependent. For example, crude oil may be made up of hundreds of chemical components. Such components may include various empirical forms and isomers of chemical compounds including, for example, alkanes, aromatics, olefins, napthenes, and other compounds. The refining process may generally change the chemical make-up of crude oil in ways that may also be batch and/or process dependent. Refining processes may include, for example, distillation, coking, hydrocracking, fluidized catalytic cracking (FCC), alkylation, de-sulfurization, reforming and isomerization. Some refining processes may also rely on catalysts, such as platinum, and other process variables, such as temperature and pressure to effect conversion. Other refining processes may take a processed composition and add the processed composition together with one or more other processed compositions or fuel components without changing the underlying chemical make-up of the mixing compositions. For example, the refining process may include one or more blending operations.
During the refining process, product components may be changed in ways so as to meet a certain set of desired properties. For example, each product may have various chemical and physical properties that particularly relate to that product's usefulness. Some of those properties may be related to one or more particular components such as benzene. Other properties may be more generally related to a distribution of components in the overall fuel composition, such as specific gravity. For example, increasing octane may be useful in reducing engine “knocking” when burned, and reducing sulfur may result in lower levels of harmful sulfur dioxide, a combustion by-product. For some refining operations, a plurality of properties may change together, often in ways that are difficult to predict, thus complicating the refining process.
For some refinery products, the refining process may include one or more blending operations wherein various intermediate products and fuel components or additives are mixed to create a finished refinery product. For example, components may be added to an unfinished fuel composition to adjust properties of the composition. Generally, it may be desirable to adjust a composition's properties in a controlled manner to more efficiently lead to a useful finished fuel product. For example, adjustment of large property value shifts may be difficult or costly. Unfortunately, current methods for monitoring and estimating properties of fuels are insufficient. Accordingly, there is generally a need for improved methods of qualifying fuels or measuring fuel properties at different stages in production, and in particular for reducing property value shifts during blending operations.
Qualification of fuels is further complicated because some fuel components may be added at different stages of a product's distribution chain. For example, some components may be added to an unfinished fuel composition at a refinery where adjustment of fuel properties may be more readily accomplished. However, other components may be added at various stages along a distribution chain after leaving a refinery. For example, adding ethanol may tend to increase risk that a fuel transported in a pipeline may become contaminated such as with water. Accordingly, ethanol is typically added downstream of a refinery at a stage at which adjustment of fuel properties is more difficult. Unfortunately, optimal techniques for estimating properties of fuels prior to final addition of components are lacking. For example, current methods for estimating the properties of not-yet finished fuels may be inaccurate or highly labor intensive. Accordingly, there is generally a need for improved methods of measuring fuel properties at different stages in the production and distribution lifetime of a fuel.